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Old May 29, 2011, 04:14 AM
Old age is not for sissies
Azarr's Avatar
Dayton Intl, Ohio, United States
Joined Jan 2000
8,034 Posts
Quote:
Originally Posted by ajbaker View Post
2. Well, yes. If you want to make your task easy, use one of THESE. It has more features than you need. But, it will do anything that you desire.

AJ
Thanks for the suggestion, but I can do all the adjustments in my transmitter.

Azarr
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Old May 29, 2011, 04:26 AM
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Joined Apr 2010
564 Posts
Quote:
Originally Posted by ajbaker View Post
That is precisely what I want to do. Since we have shared ideas together several times, you figured out what I was up to right away. Some people lack imagination. Your suggestion is perfect for my needs. Thank you very much for your input. Also, I am planning on getting rid of the LG and never setting up ailerons and flaps. I am pretty sure I can still balance it using a 1500mah LiPo. I will use whatever it the lightest I can use and still get CG. With several other weight reduction methods, I think I can get the FC below 33 oz. Of course, I will start with a brand new one. I will order just the foam stuff because the rest of the stuff I need, I can build a lot lighter. Thanks again for your feedback.
AJ
Interested in how you're going to mount the motor? Lightweight appeals to me, mine is just under 900g (say 30oz) with the small battery but fully fitted out in other respects. Losing the gear will knock off another 60/70g I suppose, 40g for the four servos and leads, maybe a smaller ESC and receiver.
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Old May 29, 2011, 05:40 AM
T.ing to put on air 100 models
chiloschista's Avatar
Switzerland
Joined Feb 2008
696 Posts
Hi all,

I know motor vibration was discussed a lot here, but I would like to share another experience.
After tenth of successful flights I started to experience motor vibrations.
I balance propellers, but even with unbalanced propellers I don't believe vibrations could become so strong and bad.
I cross swapped three different motors, three different ESCs, and three propellers. Always the same problem.

So I did a little of reading here and found someone had similar problems.

My guess is that after sometime the original motor mount deforms (temperature, air, humidity, etc. Do you know plastic loose weight becoming dry ?) and will no more hold the motor flat and stiff.

Guess what ? I fixed the motor with two more screw (so four now) and all the vibrations went away.
So what's that now ?

Even a very small amount of unbalanced propeller / motorcase will cause a resonance, or better said a wave, from front side (propeller) and backside (motorcase), the motormount being the nodal point (are you familiar with sound physics ?). It is almost impossible to stop a single wave vibration / sound in a nodal point. Fortunately sounds have harmonics which will not all pass through the same nodal point. I guess a motor - motormount - propeller system does not have noticeable harmonics.
So if the motor is not very stiff it will vibrate like a jackhammer when resonance is induced.
I had exactly the same problem in an Acromaster, but there I fixed it fixing the motor mount with four screw.

Btw on the FunCub too I discarded the two fixing screw and fixed now the motor mount to the plastic in the fuselage with four Parker like screw and washers, instead the four adjustement screw, to have the right amount of side / down thust.

Here is a link about nodal points

Thanks to everyone who wrote about this (and all the rest too ) and hope this will help others.

Best regards,

Ric
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Old May 29, 2011, 07:19 AM
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bubbleman's Avatar
Joined Jan 2007
567 Posts
Quote:
Originally Posted by mbreslin View Post
How far did you guys extend the linkage cover/tubes toward the rear of the plane? Just long enough to fill the groove and the rest just the bare wire?

Thanks.
I had the same question. The instruction to "cut to length" with no length specified is lame.

I cut the outer sleeve to the point where the groove in the fuse side started to get shallow. The inner sleeve was cut so that it was as close to the elevator/rudder horn as possible without causing interference at full deflection.

When you get to the point of stickers on the sides, depending on how far back you put them, you will have to cut out the space between the bars to clear the rod assembly.

Anton
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Old May 29, 2011, 07:41 AM
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Jurgen Heilig's Avatar
53859 Niederkassel, Germany
Joined Sep 2000
18,790 Posts
Quote:
Originally Posted by aesmith View Post
...
Losing the gear will knock off another 60/70g I suppose, 40g for the four servos and leads, maybe a smaller ESC and receiver.
Without landing gear, ailerons and flaps, the Fun Cub is no longer a Fun Cub. You would be much better off with an EasyGlider Pro then.

Jürgen
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Old May 29, 2011, 08:08 AM
did a reversed Immelman..once.
SKYPILEIT's Avatar
Novi, Michigan
Joined Nov 2002
2,254 Posts
Quote:
Originally Posted by chiloschista View Post
Hi all,

I know motor vibration was discussed a lot here, but I would like to share another experience.
After tenth of successful flights I started to experience motor vibrations.
I balance propellers, but even with unbalanced propellers I don't believe vibrations could become so strong and bad.
I cross swapped three different motors, three different ESCs, and three propellers. Always the same problem.

So I did a little of reading here and found someone had similar problems.

My guess is that after sometime the original motor mount deforms (temperature, air, humidity, etc. Do you know plastic loose weight becoming dry ?) and will no more hold the motor flat and stiff.

Guess what ? I fixed the motor with two more screw (so four now) and all the vibrations went away.
So what's that now ?

Even a very small amount of unbalanced propeller / motorcase will cause a resonance, or better said a wave, from front side (propeller) and backside (motorcase), the motormount being the nodal point (are you familiar with sound physics ?). It is almost impossible to stop a single wave vibration / sound in a nodal point. Fortunately sounds have harmonics which will not all pass through the same nodal point. I guess a motor - motormount - propeller system does not have noticeable harmonics.
So if the motor is not very stiff it will vibrate like a jackhammer when resonance is induced.
I had exactly the same problem in an Acromaster, but there I fixed it fixing the motor mount with four screw.

Btw on the FunCub too I discarded the two fixing screw and fixed now the motor mount to the plastic in the fuselage with four Parker like screw and washers, instead the four adjustement screw, to have the right amount of side / down thust.

Here is a link about nodal points

Thanks to everyone who wrote about this (and all the rest too ) and hope this will help others.

Best regards,

Ric
Good info to share..Thanks Ric..!
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Old May 29, 2011, 09:42 AM
Argue for your limitations
ajbaker's Avatar
Lincoln, CA
Joined Oct 2006
8,424 Posts
Wht kind of radio do you have?

Quote:
Originally Posted by Azarr View Post
Thanks for the suggestion, but I can do all the adjustments in my transmitter.

Azarr
Yeah. I remember now that you put that in your post. Thanks for pointing out my mistake. I will make sure not to recommend that again. In fact, I can learn something here to share with others if you would tell me what transmitter (&rcvr) you have. TIA

Handling the timing of a servo is very cool. Since the most feature rich transmitter that I have is a TH-9X, I don't see that kind of option. Now, just watch. Someone will tell me that I can do it with mine.
AJ
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Old May 29, 2011, 09:57 AM
Argue for your limitations
ajbaker's Avatar
Lincoln, CA
Joined Oct 2006
8,424 Posts
Lightweight FC

Quote:
Originally Posted by aesmith View Post
Interested in how you're going to mount the motor? Lightweight appeals to me, mine is just under 900g (say 30oz) with the small battery but fully fitted out in other respects. Losing the gear will knock off another 60/70g I suppose, 40g for the four servos and leads, maybe a smaller ESC and receiver.
First, to answer your question. I will mount a MicroDan motor (34g or 54g - undecided right now) using the mount that comes with it on a 1/8" ply mount. I could modify the existing MPX mount. But, it is too heavy and kind of a junky design anyhow. Then, of course, no paint or decals. All of it will be put together with thin CA. Packing tape will cover the spar (rear spar will not be used) to cut down on drag. There are many more things that I plan to change that are too long to list here. If you were going for lightweight, I would probably suggest using PMing because it is a fairly esoteric project. Also, it would eliminate one person whose opinion and help I don't ever want to see (quoted or not). Besides, I would run ALL of my plan past Prof100 and NoFlyZone because of their extensive experience and most of all their positive communication skills. With those two, I could suggest making the FC a pusher and they would entertain the idea. Thanks guys.
Now, I have a question. I can see how you could get down too 900g if you used a 1500mah LiPo. Is that what you used? Or, what did you use and how hard was it to get the correct CG? Thanks for any information you can share.
AJ
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Old May 29, 2011, 09:59 AM
Too much is just not enough...
Woody_99's Avatar
Joined Jan 2009
1,090 Posts
I'm thinking of joining in on the Fun Cub fun. I scanned some of the post looking for suggestions on motor and prop, but must have missed them.

Could anyone recommend a good motor and prop for the Fun Cub? I plan on using 3s 2200's and I have some 30 and 40 amp esc's.

Thanks!
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Old May 29, 2011, 10:07 AM
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1911tex's Avatar
Joined Nov 2010
287 Posts
Woody 99: Here you go .... available specifically for the Fun Cub as a Multiplex accessory with 13x4 prop. You cannot go wrong.
http://www.maxxprod.com/pdf/HC3516-0840.pdf
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Old May 29, 2011, 10:14 AM
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Prof100's Avatar
Canton, Michigan USA
Joined Jul 2007
16,651 Posts
Quote:
Originally Posted by ajbaker View Post
That is precisely what I want to do. Since we have shared ideas together several times, you figured out what I was up to right away. Some people lack imagination. Your suggestion is perfect for my needs. Thank you very much for your input. Also, I am planning on getting rid of the LG and never setting up ailerons and flaps. I am pretty sure I can still balance it using a 1500mah LiPo. I will use whatever it the lightest I can use and still get CG. With several other weight reduction methods, I think I can get the FC below 33 oz. Of course, I will start with a brand new one. I will order just the foam stuff because the rest of the stuff I need, I can build a lot lighter. Thanks again for your feedback.
AJ
AJ,

FYI, the stock, recommeded motor from Multiplex is 150 grams. The battery, with a lightweight 54 gram MicroDan, will have to move way forward.

Bill
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Last edited by Prof100; May 29, 2011 at 10:39 AM.
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Old May 29, 2011, 10:34 AM
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guy hanson's Avatar
Joined Jan 2011
745 Posts
Reducing weight on a model such as this ,can be pretty elusive.
The reason is because FIXED weight aft the center of gravity is just about impossible to change and variable weight (forward the cg) must add up to original specs.

Bottom line If you want to really reduce weight you will have to core out much of the structural foam aft the cg.
This is often counterproductive as rigidity /strength are drastically compromised .
Many kits with servos in the rear and sheet wood tail groups can be seriously lightened in th e rear sections.
The EPP type foam ones are another breed of cat. I am enclosing a typical example of futility
the 42 gram model was punched full of holes - removing 2.5 grams - a whisk of spray glue and lightweight food wrap -brought weight back up a gram.
But loosing weight is always a good thing - just don't expect much real change on the Fun Cub
realistic flying weight with strong performance -inc good battery ,won't fall much under 38 ounces.
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Last edited by guy hanson; May 29, 2011 at 10:39 AM.
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Old May 29, 2011, 10:41 AM
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Prof100's Avatar
Canton, Michigan USA
Joined Jul 2007
16,651 Posts
Quote:
Originally Posted by guy hanson View Post
Reducing weight on a model such as this ,can be pretty elusive.
The reason is because FIXED weight aft the center of gravity is just about impossible to change and variable weight (forward the cg) must add up to original specs.

Bottom line If you want to really reduce weight you will have to core out much of the structural foam aft the cg.
This is often counterproductive as rigidity /strength are drastically compromised .
Many kits with servos in the rear and sheet wood tail groups can be seriously lightened in th e rear sections.
The EPP type foam ones are another breed of cat. I am enclosing a typical example of futility
the 42 gram model was punched full of holes - removing 2.5 grams - a whisk of spray glue and lightweight food wrap -brought weight back up a gram.
But loosing weight is always a good thing - just don't expect much real change on the Fun Cub
realistic flying weight with strong performance -inc good battery ,won't fall much under 38 ounces.
Yes, but a 100 gram difference in motor weight in the nose is significant.
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Old May 29, 2011, 11:29 AM
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Jurgen Heilig's Avatar
53859 Niederkassel, Germany
Joined Sep 2000
18,790 Posts
Quote:
Originally Posted by Prof100 View Post
AJ,

FYI, the stock, recommeded motor from Multiplex is 150 grams. The battery, with a lightweight 54 gram MicroDan, will have to move way forward.

Bill
The recommended motor for the FunCub weighs 132g and has a 5mm motor shaft.

While a light motor makes sense in an aerobatic competition model (like a 12g motor in a 100g F3P model), it makes no sense to put a 34g motor in a sports model weighing approx. 1000g. Putting the same motor in a high performance glider with retractable motor pod and it may make sense again.

Jürgen
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Old May 29, 2011, 11:43 AM
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745 Posts
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Originally Posted by Prof100 View Post
Yes, but a 100 gram difference in motor weight in the nose is significant.
If the model still balances as intended and provides power required on props which deliver best thrust at desired speeds using best weight/power batteries - sure -
but honestly- a hundred gram lighter motor has to give up something. so far the best lighter motors ( for performance type small 3D etc.,) I have used are Skorpians
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